Alaska's Senate voted to approve the measures this week. They had earlier been approved by the House. They now go to Alaska Gov. Sean Parnell for signing.

The law allows cruise ships to discharge ammonia from human waste and heavy metals dissolved from ship plumbing, as there is no current technology to completely eliminate them. Such discharges would have been restricted starting in 2015 by the voter initiative passed in 2006.

The initiative made standards for cruise ships more stringent than for municipal waste treatment. The legislation was designed to create a level approach for all types of discharges, said legislators who supported it.

Under the law, ships that carry at least 250 passengers and have advanced wastewater treatment systems are allowed to meet water-quality standards at the edge of a "mixing zone" rather than at the point of discharge.

A mixing zone is the area where treated wastewater mixes with a body of water, according to the Alaska Cruise Association.

The new legislation also sunsets an advisory panel on cruise ship wastewater created in 2009.